Automatic dump for backwashing fuel filter



Feb. 26, 1957 R. c. DARNELL 2,782,932

AUTOMATIC DUMP FOR BACKWASHING FUEL FILTER Filed Jan. 25, 1954 2 Sheets-Sheet l i INVENTOR. Fax C. DARNELL BY M mxw uwm HTTOE/VEYS Feb. 26, 1957 R. c. DARNELL 2,782,932

AUTOMATIC DUMP FOR BACKWASHING FUEL FILTER Filed Jan. 25, 1954 2 Sheets-Sheet 2 HIGH PRESSURE LOW messy/e5 F/L TER I 6. INVENTOR. AEX C DARNELL.

BY x 76am, M, Z M

HTTOINEYS AUTGMATIC DUMP FOR BACKWASHING FUEL FELTER Rex C. Darnell, Dexter, Mich, assignor to Michigan Wire Cloth Company, Detroit, Mich, a corporation of Michigan Application .Fanuary 25, 1954, Serial No. 405,709 4 Claims. (Cl. 210-167) This invention relates to fuel filters and particularly to fuel filters for jet engines. In my prior application on a fuel filter, Serial No. 387,568, filed October 22, 1953, l have described and claimed a new fuel filter for jet engines which embodies a cylindrical cage supporting a screen and using a rotating member on the inside of the cage which connects successive areas on the inside of the screen with the low pressure line in the fuel supply line for the purpose of successively backwashing or purging the inside of the screen to keep the same free of contamination. This prior application is directed largely to the combination of this backwashing filter and a centrifuge separator for separating the foreign matter before the fuel is returned to the low pressure side of the high pressure pump. This filter also contains what is believed to be a novel arrangement for controlling the valve opening in the line that takes the stream of fuel that does the purging. This enables the volume of the stream to be controlled in accordance with the pressure in the high pressure line so as to make the volume used in purging substantially constant regardless of the pressure in the high pressure line. There is another similar valve control to regulate the volume of liquid which drives the hydraulic motor which in turn rotates both the centrifuge and the rotating member on the inside of the filter screen and cage. A diferential planetary reduction gearing is interposed between a tube that directly connects the centrifuge to the rotor of the hydraulic motor and a second tube which is on the outside of the first mentioned tube and which drives the rotor of the filter cage at a greatly reduced speed.

in this filter of my prior application a novel arrangement is provided in the valve and valve casing that controls the purging stream so that the valve is momentarily violently driven closed and against its valve seat several times a second so as to smash or break any ice or material that may seek to cling to the valve or valve seat.

My new improvement to be described and claimed in this application operates in connection withthe valve and its control mechanism to dump or purge the valve chamber at every revolution of the filter rotor. This assures that any ice or other contaminants which might otherwise collect on the valve, the valve seat or in the valve chamber are washed out and into the low pressure line at every revolution of the rotor. Referring to the drawings:

Fig. 1 is a longitudinal section of the fuel filter.

. Fig. 2 is a fragmentary section taken on the line 3-3 of Fig. 1.

Fig. 3 isa section through the telescoped tubes on the line 3-3 of Fig. 1.

Fig. 4 is a section on the line 4-4 of Fig. 2.

Fig. 5 is an elevation of the dumpcontrol plate.

Fig. 6 is a diagrammatic view showing the arrangement of the pumps, the filter and the fuel line.

The fuel comes in through the port 1 and passes through the filter easing into the inside of the filter cage 2. The inside of this cage is provided with a slight boss that forms the raceway 3 provided with a plurality (usually 60) slots 2,782,932 Patented Feb. 26, 1957 5. These slots connect with the flutes 6 between the fins 7. These fins support the filtering material here shown as a screen 8.

The rotor is designated 9 and this rotor is hollow inside forming the valve chamber 10. The valve seat is provided on the end of the arbor 11. The outside end is bulbous to form a ball 12 to rockingly support the rotor shoe 13. This shoe has a passageway 14 with an end which is caused to travel over the inside or raceway of the filter cage and successively connect this passageway and the valve chamber with the 60 some slots or ports in the valve cage. In other words, small areas of the screen (the flutes) are successively and individually connected with the valve chamber which by means of the slots 15 and 16 in the tubes 17 and 18 connect with the inside of the inner tube 18. This inner tube is directly coupled with the centrifuge member 19. The centrifuge is rotated by a hydraulic motor or any other suitable motor. One such hydraulic motor is shown and described in my prior application and need not be here shown and described.

This motor drives the centrifuge at between 2,000 and 3,060 revolutions a minute. It is desirable to rotate the filter rotor at only about 8 /2 revolutions a minute. Consequently, reduction gearing has to be provided. A differential planetary reduction gearing is shown at 20. It need not be described in detail here because it is described and shown in detail in my prior application. it is sufiicient to say that this or any other reduction gearing that will get this large speed reduction, something like 353' to 1, will do.

The valve control for the purging stream is described and claimed in my prior application. It consists of piston 21. This is ordinarily seated against the ring 22 by means of the high pressure fiuid entering into the chamber 23 behind the piston and driving it against the ring 22. The pressure comes through the passageway 24 which connects with fuel on the inside of the cage. This high pressure fuel is also against the valve head 25. This valve head 25 connects with the valve itself 26 by telescoping over the valve stem 27. Trapped between the valve head andthe body of the valve is a flanged cup 41. On the outside of this cup are two springs, a light weak spring 28 and a rather heavy strong spring 29. The light spring seats against the flange of the cup and the heavy spring against the ring 36. The fuel coming through the rotor is the backwashing fuel. This fuel does not have has high a pressure as the fuel bearing against the valve head in the chamber 23 and against the piston 21. The reason for this is that the passage through the filter screen and through the flutes, slots, the rotor shoe and arbor has put somewhat of a drag on the fuel and reduced its pressure slightly, something like 5 pounds if the pressure in the high pressure line is 300 pounds per square inch. Hence there is ample differential pressure to drive the valve closed, but this is not accomplished because the two springs are nicely calculated to operate against this pressure differential to keep the valve a measured opening so as to diminish the size of the backwashing stream as the pressure in the high pressure line goes up. if the operating pressure of the jet engine is low, say pounds per square inch, there will be quite an appreciable valve opening, but if the pressure is' very high, the opening will be only a few tl'rousandths of an inch. The twosprings yield to just suit the valve opening to the high pressure in the line. Where the pressure in the li'neis relatively low the weak spring does this yielding, but when high pressures are involved the weak spring is collapsed and the strong spring takes over. This will yield only minutely to the rise in pressures.

As explained in my prior application, whenever the shoe and its passageway end are opposite the bridges between two of the ports in the cage, the passageway 14 will be entirely out off from the valve chamber and the interior of tubes 17 and 18. In this situation they are cut off from the low pressure side of the high pressure pump. The high pressure may be some 300 pounds while the pressure on the low pressure side of the pump may be only 45 pounds. So when the port 14 is completely closed by reason of straddling one of the bridges in the cage the underside of the valve is suddenly blocked from the backwashing pressure. Consequently, there is momentarily a very heavy pressure differential that will drive the valve closed with a smashing action. This will crush and dislodge any ice or foreign matter. Inasmuch as there are 60 of these bridges and the rotor and shoe revolve 8 /2 revolutions a minute, there is something over 510 times a minute when a bridge is being crossed by the shoe. Dividing the 510 bridge passes a minute by 60 to reduce the figures to seconds and We have 8 /2 times a second the valve is momentarily violently closed. This gives a continuous pulsating action. It is calculated to prevent any deposit of globules of ice on the valve and the valve seat and smash these if they are present.

Right here is where the improvement which is claimed in this application, takes hold. It is desirable to clear this valve chamber periodically of the ice and foreign matter which may collect here. To this end I have provided a very simple arrangement, whereby every time the rotor completes a cycle it automatically opens wide the valve so momentarily the valve opening area may be from 50 to 70 times as much as in the normal position. This is accomplished by means of a dumpingcontrol plate shown in Fig. 5. This plate is designated 32. It contains a C groove 33 which at the back of the C has an outlet 34 that opens the C groove to the interior of the filter cage as is shown in Fig. 1. At the mouth of the C groove is a radial groove 36. A pin 37 fastens the dump control plate to the body of the filter cage. The rotor 9 is pressed up against the dump control plate by means of spring 38. This rotor has an oblique passageway 39 which at every revolution of the rotor has one end register momentarily with the radial groove 36. This radial groove will that very instant also register with the end of the passageway 40 which with passageway 24 leads behind the piston 21. At the same time the end of passageway 39 in the rotor turns opposite the radial slot 36 in the dump control plate so as to connect passageways 40 and 24 leading to the space behind the piston. Passageway 39 discharges the high air pressure behind the piston 21 through port 39a in the outer tube and through port 16 in the inner tube-the latter rotating so fast that for all practical purposes it is in constant registry with the port 39a in the slow moving tube. So here momentarily the high pressure fuel is cut ofi from the piston end of the valve and there is a free passageway between the chamber behind the piston and the low pressure side of the fuel line. High pressure is still applied to the conical end of the valve. Immediately the fuel back of piston escapes and the piston flies back against the head of the cylinder in which it is contained because momentarily there is a great pressure differential tending to force the piston away from the springs. The valve flies open. The valve opening area is now something like 50 to 70 times greater than when the valve is in its normal position. This immediately flushes or dumps the contents of the valve chamber into the low pressure line and clears the chamber, the valve, the valve seat of all the ice particles or other particles that may have collected, depositing them into the sump through the medium of the centrifuge. When the rotor turns to again bring the passageway 40 in registry with the C groove 33, the chamber behind the valve head and the piston is in communication with the interior of the cage and the high pressure. The piston returns to its normal position against the ring 22 and the valve returns to its normal position.

What I claim is:

1. In a fuel filter which has a slotted cage and a filter secured on the slotted cage and a rotor rotating in the cage to successively bring the slots or successive areas in communication with the low pressure side of the pump in a fuel supplying system while the outside of the cage has its major area exposed to the pressure of the fuel on the high pressure side of the pump, the combination of a valve casing for location in the rotor, 21 rcciprocable valve in said casing, means for controlling the opening of said valve responsive to the pressure of the high pressure fuel and dumping means for periodically automatically opening the valve by releasing the high pressure fuel acting on the control means and substituting action of the low pressure on the control means and valve to thereby momentarily widely open the valve and flush the valve chamber.

2. The combination claimed in claim 1 in which the valve control means is a piston and one or more springs, the valve reciprocating in the piston and having its position controlled by the fuel pressure differential of the unfiltered fuel and the filtered fuel and the springs acting upon the piston.

3. The combination claimed in claim 1 in which the means for releasing the valve control is a stationary dumping control plate with a large C groove with an outlet to the interior of the cage and a radial groove in the plate at the mouth of the C groove, the said rotor being pressed against this plate, the said rotor being provided with a body having one passageway connected with the the interior of the rotor and having an end which registers for most of the cycle with the C groove to thereby put the pressure in the interior of the cage behind the valve and the valve control mechanism, the body of the rotor also provided with a second passageway which momentarily at each cycle of the rotor registers at one end with the radial groove of the dump control plate and with an inlet to the low pressure side of the fuel line at which time the first mentioned passageway is also in registry with the radial groove in the control plate to thereby open the chamber behind the valve in the valve control mechanism to the low pressure side of the fuel line and thereby momentarily dump and purge the contents of the valve chamber.

4. The combination claimed in claim 3 in which the means for controlling the valve opening is a piston nor mally held against a stop by the pressure diiferential between the purified fuel and the unpurified fuel and the valve is slideable in said piston, one or more springs pressing against said piston and acting against the pressure differential holding said piston in a definite position with respect to the valve seat.

References Cited in the file of this patent UNITED STATES PATENTS 1,028,789 Rothwell June 4, 1912 1,585,817 Bailey et al. May 25, 1926 2,066,479 MacIsaac Jan. 5, 1937 2,441,526 Zollinger May 11, 1948 2,656,847 Collins Oct. 27, 1953 FOREIGN PATENTS 563,831 Great Britain Aug. 31, 1944 

